A stator of a poly-phase electric motor typically undergoes electrical testing during manufacturing. Surge testing is one such test. During conventional surge testing, a capacitor is rapidly discharged to inject a voltage surge into the phase leads of the stator. This rapid electrical discharge produces a sinusoidal wave for one or more phases of the electric motor. The voltage surge stresses the stator's insulation, and thus can be used to detect electrical shorts or other potential insulation issues.
In a bar-wound stator, conductive coils of wire are replaced with solid copper bars known as “hair pin” conductors. The hair pins are individually inserted into slots of a laminated stack of the stator. The hair pins are generally configured with a curved section terminating in a pair of wire ends and are formed into a shape suitable for insertion into the stator slots. An insulating material is used prior to insertion of the hair pins in the stator slots such that adjacent surfaces of the hair pins are electrically insulated with respect to each other and from the laminated stack. Portions of the wires protruding from the laminated stack after insertion of the hair pins are bent or twisted to form a complex weave pattern, thereby creating wire end pairs. Adjacent wire end pairs are typically welded together at one side of the laminated stack to form the required electrical connections/circuits between the various layers of the stator.